compiler: cache modules if they are not built yet

compiler/cc.v

@@ -111,20 +111,14 @@ fn (v mut V) cc() {
 		a << '-c'
 	}
 	else if v.pref.is_debug {
+		vexe := os.executable()
 		builtin_o_path := '$v_modules_path/vlib/builtin.o'
 		if os.file_exists(builtin_o_path) {
 			libs = builtin_o_path
 		} else {
-			println('$builtin_o_path not found... build module builtin')
+			println('$builtin_o_path not found... building module builtin')
+			os.system('$vexe build module vlib/builtin')
 		}
-		// '$v_modules_path/vlib/strings.o '+
-		// '$v_modules_path/vlib/math.o '
-		/*
-		if !os.file_exists(libs) {
-			println('object file `$libs` not found')
-			exit(1)
-		}
-		*/
 		for imp in v.table.imports {
 			if imp == 'webview' {
 				continue
@@ -134,7 +128,8 @@ fn (v mut V) cc() {
 			if os.file_exists(path) {
 				libs += ' ' + path
 			} else {
-				println('$path not found... build module $imp')
+				println('$path not found... building module $imp')
+				os.system('$vexe build module vlib/$imp')
 			}	
 		}
 	}

compiler/fn.v

@@ -419,8 +419,8 @@ fn (p mut Parser) fn_decl() {
 		p.genln('pthread_mutex_lock(&live_fn_mutex);')
 	}
 
-	if f.name == 'main__main' || f.name == 'main' || f.name == 'WinMain' {
-		if p.pref.is_test && !p.scanner.file_path.contains('/volt') {
+	if f.name in ['main__main', 'main', 'WinMain'] {
+		if p.pref.is_test {
 			p.error_with_token_index('tests cannot have function `main`', f.fn_name_token_idx)
 		}
 	}

compiler/parser.v

@@ -1686,6 +1686,7 @@ fn (p mut Parser) bterm() string {
 
 // also called on *, &, @, . (enum)
 fn (p mut Parser) name_expr() string {
+	//println('n')
 	p.has_immutable_field = false
 	p.is_const_literal = false
 	ph := p.cgen.add_placeholder()
@@ -2958,7 +2959,7 @@ fn (p mut Parser) map_init() string {
 		mut i := 0
 		for {
 			key := p.lit
-			keys_gen += 'tos2((byte*)"$key"), '
+			keys_gen += 'tos3("$key"), '
 			p.check(.str)
 			p.check(.colon)
 			p.cgen.start_tmp()

vlib/builtin/map.v

@@ -177,6 +177,7 @@ pub fn (m &map) keys() []string {
 }
 
 fn (m map) get(key string, out voidptr) bool {
+	//println('g')
 	if m.root == 0 {
 		return false
 	}

vlib/os/os.v

@@ -333,6 +333,7 @@ pub fn exec(cmd string) ?Result {
 	}
 }
 
+// `system` works like `exec()`, but only returns a return code.
 pub fn system(cmd string) int {
 	mut ret := int(0)
 	$if windows {